When Best Buy first announced earlier this morning that its CEO Brian Dunn had decided to resign, the move was not unexpected. The big US electronics store chain has reported just a few days ago that its revenues were below expectations and that 50 of its stores would be closed.

And then things got more interesting. The Wall Street Journal is now reporting that Dunn left after Best Buy started conducting an investigation into his "personal conduct". In a statement, Best Buy said:

Certain issues were brought to the board's attention regarding Mr. Dunn's personal conduct, unrelated to the company's operations or financial controls, and an audit committee investigation was initiated. Prior to the completion of the investigation, Mr. Dunn chose to resign.

Best Buy offered up no further details on their investigation. Dunn, who worked at Best Buy for 28 years and became its CEO in 2009, has yet to comment on Best Buy's new announcement. In a statement this morning in Best Buy's original press release, Dunn said, "I have enjoyed every one of my 28 years with this company, and I leave it today in position for a strong future. I am proud of my fellow employees and I wish them the best."

Best Buy has named one of its board members, G. Mike Mikan, as its interim CEO until a permanent replacement is named.